Exposure Charts to Fluoro Flashcards
When should exposure charts be updated?
Annually or if there has been a change in processing equipment- speed of films/ devices
What is the main disadvantage of a fixed mA system?
as kV increases, contrast and resolution decreases
Fixed mA formula
2kVp X part cm + 30kVp = New kVp
Edison built 4 portables in what year?
1896
Conventional fluoro uses what type of screen?
fluorescent
A flourescent screen in conventional fluoro converts ______ to ______?
photons to visible light
A flourescent screen in conventional fluoro creates a _______, which is a real time visible image.
hologram
Conventional fluroscopy created a high or low patient/viewer dose?
HIGH- flouro time was longer
What are the 3 tubes included in Image Intensified Fluoro?
Image intensifier, TV Camera Tube, Cathode Ray Tube (CRT/Monitor)
What are the 3 benefits of image intensified fluoro?
improved brightness levels, improved visual acuity/contrast, lower patient exposure
Glass Envelope is made of what?
pyrex
Input Phosphor screen is made of what?
Cesium Iodide
What does the input phosphor screen convert?
converts invisible photons entering image intensifier tube to visible light
What are the possible dimentions for a dual and tri focused input phosphor screen?
dual- 6-9”
tri- 4/7/10”
Photo Cathode is made of what in the image intensifier tube?
Antinomy Sulphite
What does the photo cathode convert?
converts visible light to electrons
What is the charge of the electrostatic lenses?
negative
What do the electrostatic lenses do?
focus electrons from input screen to output screen
What is the electron focal spot?
point that electrons crossover and intersect during travel inside the tube
When does the electron focal spot change?
when kV changes
Output phosphor screen is made of what?
Zinc Cadmium Sulfide
What does the output phosphor screen convert?
electronic image back to visible image
What is the normal size of the output screen?
1in
What is the purpose of the aluminum filter?
prevents light that bounces back from going into tube: MIRROR
How many times brighter is the image coming from image intens fluoro compared to conventional?
5,000-10,000 times brighter
What is the brightness gain formula?
BG= Flux Gain X Minification Gain
What is the definition of flux gain?
gain in brightness from tube potential- as kV increases, brightness and flux gain increases
What is the definition of minification gain?
ratio of input screen (squared) : ratio of output screen (squared)
ex: 9^: 1^
Definition of contrast resolution
ability to see differences in densities and tissue opacities
Definition of spatial resolution
ability to discern between line pairs/ structures
As size of input screen _______, spatial resolution _______
increases, decreases
As size of input screen __________, vignetting ___________
increases, increases
Definition of vignetting
reduced brightness/ blur at image periphery
Definition of Automatic Brightness Control
maintains image quality/ brightness when part thickness changes
What is the line pair/ mm spatial resolution for a 9” input screen?
1-2 line pairs/ mm
What is the line pair/ mm spatial resolution for a 4” input screen?
6 line pairs/ mm
Image quality in a fluroscopic image refers to what 2 traits?
resolution and magnification
Small Field size in image intens fluoro gives what 3 image quality traits?
improved magnification
improved resolution
increased patient dose
Higher kv in image intens fluoro gives what 3 image quality traits?
improved magnification
improved resolution
greater image brightness
Higher mA in image intens fluoro gives what 3 traits?
higher resolution
greater brightness
increased patient dose
What does the TV camera tube convert?
visible light to synchronous modulated signal
What is included on the target assembly end of the tv camera tube? (2)
Photocathode & Signal Plate
The photocathode is made of what in a tv camera tube (target assembly)
antinomy trisulfide
Signal plate is composed of what?
thin graphite
What does the signal plate in the tv camera tube do?
conducts electrical impulses which will be converted to synchronous modulated video signals
The opposite side of the target assembly in a tv camera tube contains what? (3)
Electron Gun, Steering Coils, Accelerator Grids
What is the electron gun composed of?
heated filament
What does the electron gun do?
directs electrons into raster pattern onto target surface to produce video signal
What type of charge do the steering coils have?
negative
What is the purpose of the accelerator grids?
provide electrical potential to accelerate electrons
The TV monitoring system (CRT) contains what 4 parts?
Gas Evacuated Tube
Electron Gun
Focusing and Deflecting Coils
Fluorescent Screen
What part of the TV monitoring system creates the image that is seen on the TV monitor?
fluorescent screen
What creates 1 Frame?
2 Horizontal Lines (1 Field) & 2 Vertical Lines (1 Field)
What is the difference in spatial resolution (lines) between standard tv and digital fluoro
525 vs 1000
Definition of vertical resolution
number of lines per frame
Definition of horizontal resolution
frequency/ how often beam is changed- measured in Hz
Horizontal resolution/bandwith for commercial TV
3.5 MHz
Horizontal resolution/bandwith for fluoro TV
4.5 MHz
Horizontal resolution/bandwith for digital fluoro
20 MHz
In a TV Monitor viewing system, what is placed between the image intensifier tube and tv camera tube?
coupled device
What is the purpose of the coupled device?
transfers and magnifies images from the intensifier tube to an optimal viewing device
3 ways in which coupling devices may be used
- Mirror Optical Viewing System
- Tandem Mirror Device (beam splitter)
- Fiber Optics
What is a lens coupling device?
system of mirrors positioned to divert beam to viewing device
How does a tandem mirror device function? (beam splitter)
tv systems are used to record image directly off image intensifier tube - beam goes in multiple directions
10-90% goes to TV Camera Tube
Other goes to TV Monitor or Recording Device
What are the 5 disadvantages of a fiber optic viewing device?
expensive
without video or viewing camera
limited fluoro viewing
cannot accommodate imaging devices
images can only be viewed and NOT recorded
What are the advantages of a TV Monitoring system?
Brightness & contrast can be manipulated
Multiple viewers
Multiple recording systems can be integrated
Digital imaging is possible
In digital fluoro, what is inserted between the video signal and tv monitor?
computer
What replaces the TV Camera tube (in imag intens), in digital fluoro?
Charged Coupling Device
What is the charged coupling device composed of?
crystalline silicon
What does the charged coupling device convert?
visible light to electrons
What is the spatial resolution of digital?
10 lp/ mm
In a digital video system, how long does it take for the beam of the tv camera tube to sweep the target assembly?
33msec= 1 frame
Signal to noise ratio: higher ratio = ______ noise
less
The analog digital converter (ADC) increases in bits, there are more signal values which creates greater ________ & ________
densities and resolution
Regarding data aquisition, as the matrix size _____, data aquisition ______
increases, decreases
as the resolution increases we can acquire less data
Digital fluoro allows these 3 different types of subtraction techniques as a great advantage
Temporal, Energy, Hybrid
Temporal subtraction in digital fluoro does what?
frame 1 is subtracted from subsequent frames to change densities/ contrast
Energy subtraction in digital fluoro does what?
removes a select spectrum of energy from K-shell absorption (photoelectric effect)
What is the greatest advantage of digital fluoro?
pulsating x-ray beam breaks up beam into smaller dose decreasing patient exposure = more info in less fluoro time
What is the spatial resolution of the PACS HR flat panel screens?
2000 lines/ frame
The 3 phase high frequency generator of digital fluoro creates what bandwidth?
90hZ (per sec)
What is the output phosphor made of?
zinc cadmium sulfide
Output phosphor converts ____ to ____
electron image back to visible light
What kV does the image intensifier tube usually run at?
80 kVp
What is the minimum required kV for the image intensifier tube to function
25 kV
What is placed at the back of the output phosphor to reduce bounceback of light
aluminum filter
brightness gain for image intensifier when compared to conventional fluoroscopy
5000 - 10,000 times brighter
formula for brightness gain
BG = flux gain x minification gain
formula for flux gain
tube potential (kV)
formula for minification gain
input screen : output screen squared ( 9^2 / 1^2 for 9 inch input and 1 inch output)
What is the standardized unit for brightness gain?
Conversion factor = Candela per meters squared / mR per second
9” input screen creates how many line pairs per mm
1 - 2 lp mm
4” input screen creates how many line pairs per mm
6 lp mm
As input screen size goes up, spatial resolution goes ___
down
Input screen size goes up, vignetting ___, brightness ___
vignetting increases, brightness decreases
what is vignetting
reduced brightness / blur at the image periphery
what maintains image quality / brightness when part thickness changes
automatic brightness control
as input screen size decreases, magnification ____
increases
as input screen size decreases, resolution ___
increases
as input screen size increases, exposure rate and dose ____
decreases
as kV is increased, magnification ____
increases
as kV decreases, resolution ____
decreases
as kV increases, image brightness _____
increases
as mA increases, resolution ____
increases
as mA increases, image brightness _____
increases
as mA decreases, patient dose ____
decreases
How does the electron focal spot move when kV is increased?
focal spot moves closer to the input screen
What happens when the electron focal spot moves closer to the input screen?
increased magnification, bightness, and resolution (loss of periphery due to divergence)
3 types of TV Camera tubes
vidicon, plumbicon, orthicon
The photocathode in the target assembly (TV camera tube) converts ___ to ____
visible light to electrons
the signal plate in the target assembly (TV camera tube) converts
electrical impulses into a synchronous modulated video signal
frequency of the synchronous modulated video signal at the end of the TV camera tube
60 Hz
what comes out of the TV camera tube
synchronous modulated video signal
raster pattern in the CRT
like a typewriter, 2 horizontal traces and 2 vertical traces from electron gun make up 1 TV picture frame
how many scanned lines are in 1 field of a raster pattern?
262.5 scanned lines in 1/60 of a second
____ fields make up 30 frames
60 fields
How many scanned lines appear every 1/30th of a second
525 lines, creating 2 interlaced fields
2 interlaced scanning fields creates ___ frames
1 frame
In digital progressive mode, how long does it take the target assembly to sweep from top to bottom?
33 msec or 0.033 sec
Number of lines of active trace per frame in standard TV
525 lines
Number of lines of active trace per frame in Digital Fluoro
1000 active lines
vertical resolution equals
lines per frame
horizontal resolution equals
frequency in Hz, which is times per second the beam is modulated
definition of noise
undesirable fluctuations in densities
causes of noise in digital fluoroscopy
fluctuations in voltage, differences in heating of filaments, interruption of a signal
signal to noise ration - higher ratio equals ____ signal and ____ noise
high signal and less noise - which is good
most common type of viewing system
TV monitoring - closed circuit with coupling devices between image intensifier and TV monitor
Lens coupling device converts
light from image intensifier to parallel beam to divert
disadvantages of lens coupling
limited viewing, single viewer, viewing one image at a time
charged coupling device is made of
crystalline silicon
charged coupling device converts
visible light to electrons
matrix size of a charged coupling device
1024 x 1024 pixels
resolution of digital charged coupling device
10 line pairs per mm
benefits of charged coupling device
high resolution, linear contrast so no densities are useless, no distortion artifacts
what is the weakest link with the weakest signal in the TV imaging chain
CRT
matrix size of digital fluoroscopy
1024 x 1024
1024 x 1024 is also known as
1000 line system
pixel size =
image intensifier size in mm / matrix size by 1 way (127 mm divided by 1024 = 0.124mm pixel size)
A high frequency generator for digital fluoro operates at ___ Hz
90 Hz instead of the traditional 60
how much mA does image intensified fluoroscopy typically use
5 mA
how much mA does digital fluoroscopy typically use
hundreds of mA
benefit of pulse progressive fluoroscopy
reduced heat overload
Charged coupling device replaces the
TV tube
How does the analog to digital converter create a video signal?
creates a binary numeric value to represent a density for transmitting to each pixel on the monitor
Digital image acquisition can take ___ images per second
1-10 images per second
How long does digital image acquisition take to produce 1 video frame?
33 ms or 0.033 sec
long exposures ___ patient dose and ___ noise
increase, increase
microprocessor (computer) image quality depends on
speed of image acquisition, image processing, post manipulation processing
what is the range of moving images and information
systemic dynamic range
Meaning of ADC
analog to digital converter
8 bit ADC = ___ analog signal values
0 - 255
10 bit ADC = ___ analog signal values
1023
As ADC bits increases, resolution ____
increases
Output of ADC is transmitted and manipulated into ___
pixel and matrix form
image acquisition, processing, and transmission depend on
dynamic range of pixels, number of pixels, method of storage
How many images per second can data acquisition get
30 images per second
As pixel matrix size increases, data acquisition ____
decreases
How many images per second can a 1024 matrix acquire?
8 images per second
PACs stands for
picture archival communication systems
